Although capsule pressure gauges and diaphragm pressure gauges differ by only one Chinese character, they are two distinct types of pressure measuring instruments with significant differences in structure, working principle, applicable media, and application scenarios.
The appearance of a capsule pressure gauge is basically the same as that of a bourdon tube pressure gauge, but its pressure-sensing element is an elastic sensitive component called a capsule. The capsule is formed by welding two circular corrugated diaphragms together. When the pressure of the measured medium acts on the capsule, elastic deformation occurs inside the capsule, and its free end produces displacement. This displacement is then amplified through a gear transmission mechanism, and the measured pressure value is indicated by a pointer on the dial.
A diaphragm pressure gauge is a system composed of a diaphragm isolator, a general-purpose pressure gauge, and a sealed hydraulic fluid. The diaphragm isolator is used to isolate the measured medium from the pressure measuring element. When the pressure of the measured medium acts on the diaphragm, the diaphragm deforms and compresses the sealed hydraulic fluid in the closed system. The transmission effect of the sealed hydraulic fluid causes the elastic element (such as a bourdon tube) in the pressure gauge to produce corresponding elastic deformation, thereby indicating the pressure of the measured medium.
Composed of a measuring system (connector, capsule element, etc.), a transmission mechanism (lever mechanism, gear transmission mechanism), an indicating component (pointer, dial), and a housing (case, gasket, and mirror glass), it has a relatively simple structure, high seismic performance, and good temperature adaptability.
Composed of a diaphragm isolator, a general-purpose pressure instrument (such as a bourdon tube pressure gauge), and a sealed hydraulic fluid system, it has a relatively complex structure but excellent corrosion resistance. It can prevent the measured medium from directly entering the general-purpose pressure gauge, avoid sediment accumulation, and is easy to clean.
